[PATCH 2/5] drm/gem: add shmem get/put page helpers

[Patrik Jakobsson]

On Sun, Jul 7, 2013 at 8:58 PM, Rob Clark <robdclark at gmail.com> wrote:
> Basically just extracting some code duplicated in gma500, omapdrm, udl,
> and upcoming msm driver.
>
> Signed-off-by: Rob Clark <robdclark at gmail.com>
> ---
>  drivers/gpu/drm/drm_gem.c | 91 +++++++++++++++++++++++++++++++++++++++++++++++
>  include/drm/drmP.h        |  4 +++
>  2 files changed, 95 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> index 443eeff..853dea6 100644
> --- a/drivers/gpu/drm/drm_gem.c
> +++ b/drivers/gpu/drm/drm_gem.c
> @@ -406,6 +406,97 @@ int drm_gem_create_mmap_offset(struct drm_gem_object *obj)
>  }
>  EXPORT_SYMBOL(drm_gem_create_mmap_offset);
>
> +/**
> + * drm_gem_get_pages - helper to allocate backing pages for a GEM object
> + * from shmem
> + * @obj: obj in question
> + * @gfpmask: gfp mask of requested pages
> + */
> +struct page **drm_gem_get_pages(struct drm_gem_object *obj, gfp_t gfpmask)
> +{
> +       struct inode *inode;
> +       struct address_space *mapping;
> +       struct page *p, **pages;
> +       int i, npages;
> +
> +       /* This is the shared memory object that backs the GEM resource */
> +       inode = file_inode(obj->filp);
> +       mapping = inode->i_mapping;
> +
> +       npages = obj->size >> PAGE_SHIFT;

Theoretical issue, but what if obj->size is not page aligned? Perhaps put a
roundup(obj->size, PAGE_SIZE) here?

> +
> +       pages = drm_malloc_ab(npages, sizeof(struct page *));
> +       if (pages == NULL)
> +               return ERR_PTR(-ENOMEM);
> +
> +       gfpmask |= mapping_gfp_mask(mapping);
> +
> +       for (i = 0; i < npages; i++) {
> +               p = shmem_read_mapping_page_gfp(mapping, i, gfpmask);
> +               if (IS_ERR(p))
> +                       goto fail;
> +               pages[i] = p;
> +
> +               /* There is a hypothetical issue w/ drivers that require
> +                * buffer memory in the low 4GB.. if the pages are un-
> +                * pinned, and swapped out, they can end up swapped back
> +                * in above 4GB.  If pages are already in memory, then
> +                * shmem_read_mapping_page_gfp will ignore the gfpmask,
> +                * even if the already in-memory page disobeys the mask.
> +                *
> +                * It is only a theoretical issue today, because none of
> +                * the devices with this limitation can be populated with
> +                * enough memory to trigger the issue.  But this BUG_ON()
> +                * is here as a reminder in case the problem with
> +                * shmem_read_mapping_page_gfp() isn't solved by the time
> +                * it does become a real issue.
> +                *
> +                * See this thread: http://lkml.org/lkml/2011/7/11/238
> +                */
> +               BUG_ON((gfpmask & __GFP_DMA32) &&
> +                               (page_to_pfn(p) >= 0x00100000UL));
> +       }
> +
> +       return pages;
> +
> +fail:
> +       while (i--)
> +               page_cache_release(pages[i]);
> +
> +       drm_free_large(pages);
> +       return ERR_CAST(p);
> +}
> +EXPORT_SYMBOL(drm_gem_get_pages);
> +
> +/**
> + * drm_gem_put_pages - helper to free backing pages for a GEM object
> + * @obj: obj in question
> + * @pages: pages to free
> + * @dirty: if true, pages will be marked as dirty
> + * @accessed: if true, the pages will be marked as accessed
> + */
> +void drm_gem_put_pages(struct drm_gem_object *obj, struct page **pages,
> +               bool dirty, bool accessed)
> +{
> +       int i, npages;
> +
> +       npages = obj->size >> PAGE_SHIFT;

Same thing here.

> +
> +       for (i = 0; i < npages; i++) {
> +               if (dirty)
> +                       set_page_dirty(pages[i]);
> +
> +               if (accessed)
> +                       mark_page_accessed(pages[i]);
> +
> +               /* Undo the reference we took when populating the table */
> +               page_cache_release(pages[i]);
> +       }
> +
> +       drm_free_large(pages);
> +}
> +EXPORT_SYMBOL(drm_gem_put_pages);
> +
>  /** Returns a reference to the object named by the handle. */
>  struct drm_gem_object *
>  drm_gem_object_lookup(struct drm_device *dev, struct drm_file *filp,
> diff --git a/include/drm/drmP.h b/include/drm/drmP.h
> index 3cb1672..7ec3fa4 100644
> --- a/include/drm/drmP.h
> +++ b/include/drm/drmP.h
> @@ -1730,6 +1730,10 @@ void drm_gem_free_mmap_offset(struct drm_gem_object *obj);
>  int drm_gem_create_mmap_offset(struct drm_gem_object *obj);
>  int drm_gem_create_mmap_offset_size(struct drm_gem_object *obj, size_t size);
>
> +struct page **drm_gem_get_pages(struct drm_gem_object *obj, gfp_t gfpmask);
> +void drm_gem_put_pages(struct drm_gem_object *obj, struct page **pages,
> +               bool dirty, bool accessed);
> +
>  struct drm_gem_object *drm_gem_object_lookup(struct drm_device *dev,
>                                              struct drm_file *filp,
>                                              u32 handle);
> --
> 1.8.1.4

Looks good otherwise, so for all 5 patches:
Reviewed-by: Patrik Jakobsson <patrik.r.jakobsson at gmail.com>